CHAPTER CI 

 THE AUTONOMIC NERVOUS SYSTEM 



In discussing the physiology of the central nervous system, we have 

 broken away from the traditional textbook treatment of the subject in 

 that we have left practically untouched any description of the course of the 

 various nerve tracts or of the position of the nerve centers. We have 

 pursued this policy in the belief that the study of these details of structure 

 belongs just as surely to the anatomist as does the structure of other parts 

 of the body, notwithstanding that to trace the course of the nervous path- 

 ways he may have to call to his aid the physiologist and clinical neurologist. 

 There is one part of the nervous system, however nam.ely, the involuntary 

 or autonomical the physiology of which it is impossible to discuss apart 

 from its anatomy, because this has depended very largely on physiological 

 methods for its elucidation. Until such methods were emphasized and 

 while anatomy alone was depended upon, little could be learned of the 

 functions and connections of the sympathetic chain and of the various 

 nerve plexus that compose the involuntary nervous system. We shall here 

 review briefly the general anatomical plan of this system as described by 

 Gaskell. 17 



GENERAL PLAN OF CONSTRUCTION 



The plan of the involuntary nervous system is much the same as that 

 of the voluntary, the main points of difference being dependent upon the 

 location of the neurons composing the reflex arcs. It will be remembered 

 that there are three of these: the receptor, the internuncial, and the ef- 

 fector neurons (page 782). The receptor neurons have the same position 

 for both systems; namely, the posterior root ganglia (Fig. 228). The inter- 

 nuncial neurons of the involuntary system, like those of the voluntary, 

 have their cells in the spinal cord, where they are represented, in the 

 thoracic region, by the cells of the lateral horn of gray matter; in the 

 sacral region, by a similarly placed collection of cells; and in the bulbar 

 region, mainly by the dorsal nucleus of the vagus. The main cause for 

 the difference between the two systems is dependent on the course of the 

 fibers of the internuncial neurons ; in the involuntary system they leave the 

 spinal cord 'before connecting Avith the effector neuron nerve cells, which 

 are contained in the various ganglia found throughout the body, whereas 



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